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Lucy: In certain type of butterfly valves, there may be both replacable seat in the body, and a replaceable seal ring on the disc edge. Triple offset metal seated valves are a good example. Typically, both the seat and the disc seal ring are replaceable (exception is Vanessa who weld stellite...

Lucy: 1) Double D flats are just two opposing flats machined to the round shaft. I guess the material removed would have a geometry of two Ds back to back, hence the double D name. 2) Seat is always in the body... Disc may have a separate sealing element attached to the disc edge, and...

Lucy: 1) I am not sure what you mean by the "pin". Pins are often used to secure the disc to the valve stem. This feature is used on all types of butterfly valves. No pins would mean that the drive between the disc and the stem is internal to the disc, such as an internal square, DD...

Lucy: More answers to your latest questions: 1)Wafer bodies are smaller on OD than lug bodies, (the of a wafer OD would be about like the inside of the flange bolt circle), the flange bolts straddle the outside of the body. You can not bolt a wafer to a single flange - wafer is squeezed...

Lucy: Here are answers to your questions from Aug. 5th. 1. tapped and not tapped flange holes in valve bodies. Generally, lug version of the body has tapped holes, which allowes direct bolting to pipe flanges without using nuts. On rare occasions, customers try to avoid tapped holes, because...

Lucy: Your initial question about the flanging seems to have exploded to many other subjects. I will try to give you answers to whatever I remember from the above thread... Re. flanged and double flanged concept. This means the same thing, i.e. the valve has a flange at each end. A...

Steve: Ouch... This is a tough service. I would also recommend the triple offset metal seated BFV, as recommended by RXH above. However, 3" size is a bit small for this type of valve, and even though some manufacturers (Tomoe) make them all the way down to 2", 3" is probably the...

Further to the triple offset (triple eccentric) butterfly valves, this geometry allows a valve construction with rigid sealing parts, i.e. metal seat which is inherently fire-safe, and cryogenic, and exhibits drop-tight (bubble-tight) sealing capability. In other words, you can reliably seal a...